"On December 7, 2004 at noon, the [Radiation Safety Officer] RSO contacted the [State of California Radiological Health Branch] Office to report a nuclear density gauge (Troxler model 3440, serial #15945) with a nominal 40 mCi Am:Be source (serial #47-11302) and a nominal 8 mCi Cs-137 source (serial #50-4969) had been stolen out of a locked construction trailer at Blossom Housing site off of Flynn Springs Road in the County of San Diego sometime between 11 am on Monday, December 6, 2004 and 7 am on December 7, 2004, when the theft was discovered. The gauge was last seen by the gauge user when he locked it up on Friday [12/03/04] at 3:30 pm in a trailer owned and used only by Geocon, Inc. A job foreman with another company reported he had noticed the trailer was locked shortly before he left the job site on Monday, December 6, 2004 at 11 am. Besides being inside the locked trailer, the case containing the gauge was locked with a padlock and the case was chained and locked to the trailer. The dead bolt lock on the trailer door had been drilled out and the gauge, gauge case, chain and lock, along with the door lock had been removed from the premises. A police report was filed with the San Diego County Sheriff's office (case #04084256A).

"A reward will be offered for the return of the nuclear gauge.

"The FBI was apparently informed of the theft by the San Diego Sheriff's office, as the licensee reported receiving a call from the FBI."

"At 1317 [hrs CST] on December 10, 2004, an automatic actuation of the reactor protection system (RPS) occurred resulting in a reactor scram. The apparent cause of the event was loss of a vital instrument bus due to a fault in a nonsafety related vital inverter. This inverter provides power to selected control room instrumentation and controls. This resulted in the loss of feed water level control.

"Reactor level is being maintained by the High Pressure Core Spray System. The feed water system is not available. Reactor pressure is being controlled through the main turbine steam bypass system to the condenser. The condenser is available and being used as the heat sink. The residual heat removal system was operated in suppression pool cooling mode to provide a means of rejecting water from the suppression pool [water input from High Pressure Core Spray System minimum flow line]. The plant is currently stable, and being maintained in hot shutdown. Systems responded as expected based on the initiating event. Reactor Core Isolation Cooling is not being used pending evaluation of a system alarm that is currently being investigated. Investigation of the initiating fault is being pursued in order to recover the vital bus and feed water level control."

It has been preliminarily determined that the loss of instrument power resulted in the Main Feedwater regulating valve failing as-is and the "B" Reactor Recirculation Pump shifting down in speed. The reduction in reactor power with constant feed flow resulted in a high reactor vessel water level, producing a direct reactor scram signal at the High Level 8 setpoint.

The licensee has notified the NRC Resident Inspector.

* * * UPDATE FROM G. HUSTON TO M. RIPLEY AT 2025 EST 12/10/04 * * *

"At 1657 CST [on 12/10/04], reactor level control was restored to the normal Feedwater and Condensate Systems. The High Pressure Core Spray System was restored to the normal standby lineup. Investigation into the cause of the reported RPS actuation continues. Investigation into the Reactor Core Isolation Cooling System alarms has resulted in declaring this system inoperable."